Thermodynamic properties are calculated by using composition models in which data obtained by analysis of the samples are integrated and by varying certain parameters such as pressure and temperature for example, from values reproducing those existing at the bottom of the bore hole to those prevailing at the surface. Analysis methods of this type allow important properties to be measured, such as the "bubbles point" indicating the appearance of a gas phase in the sample tested, the compressibility coefficient, the density, the GOR (gas/oil ratio), etc, as it is known to specialists.
A device intended for conducting measuring operations on samples is for example described in the French patent application 2,666,415 filed by the applicant. It includes a thermostatically-controlled enclosure containing two cells consisting of two cylindrical chambers defined respectively by two mobile pistons, driving means for moving the two pistons in an independant or coordinated way and a microprocessor drive system. This device allows a whole series of operations to be achieved while keeping the samples placed in the chambers under pressure and temperature conditions analogous to those prevailing in the bottom of a bore hole.
Conducting certain measuring operations requires the possibility of taking a fraction of the sample volumes contained in the study cells inside the thermostat-controlled enclosure. In order to facilitate handlings and to improve measurement precision, it is important to respect certain conditions:
Sampling must preferably be achieved under the pressure and temperature conditions prevailing in the thermostat-controlled enclosure, the sampling cell must therefore be introduced easily into the enclosure and simply coupled to the balancing cell containing the substance to be taken, before it is removed in the same way. PA0 The volume of the sample taken and the mass thereof must be known with precision in order to be able to measure easily the density thereof, and it has to be transferable almost totally to other measuring devices. PA0 Furthermore, the sampling cell must be easily detachable so as to allows visual checks. PA0 The operation of withdrawal of the fraction and of transfer to a measuring device such as a gasometer must be performed automatically so that set values may be easily accomplished. PA0 A sampling cell for containing fluids under high pressure, including a body provided with a cavity of variable volume and a first valve PA0 a fixed connection element arranged in the thermostat-controlled enclosure close to an opening provided in a wall thereof and communicating with the balancing cell by means of a second valve PA0 control, which may be operated from outside the thermostat-controlled enclosure, for introducing and fastening the sampling cell against the connection element so as to allows controlled communication between the cavity and the balancing cell; PA0 an operating assembly integral with the first connection element for varying the volume of the cavity when the sampling cell is fastened to the first connection element; and PA0 a transfer device for controlling fluid transfers between the sampling cell and devices for analyzing thermodynamic properties.